Evaluation and stability of the Patient Acceptable Symptom State (PASS) over time in patients with ankylosing spondylitis

Abstract

Objectives: The Patient Acceptable Symptom State (PASS) is the value beyond which patients consider themselves well. Our aim was to determine the PASS estimate for patients with AS by assessing pain, disease activity and functional impairment and evaluate whether the PASS is stable over time.

Methods: A 4-week prospective study of patients with AS was carried-out. The PASS was estimated at week 2 and 4 for the following patient reported outcomes: global and nocturnal pain measured on a visual analogue scale, disease activity (BASDAI), and functional impairment (BASFI). We used an anchoring method based on patients answering yes or no to, 'is your current condition satisfactory, when you take your general functioning and your current pain into consideration?' The PASS was defined as the 75th percentile of the score for patients who considered their state satisfactory. Pearson's chi square and binary logistic regression were used to analyse the data.

Results: A total of 200 patients were recruited of whom 110 (55%) were in PASS. The PASS estimates were 60 mm for global pain, 40 mm for night pain, 4.0 for BASDAI and 4.3 for BASFI. These PASS values were stable over time for all criteria except for pain. Significant contributors to PASS were low functional impairment ([BASFI]; p<0.001), low pain intensity (p=0.02), intensive physical activity (p=0.004) and high educational level (p=0.01).

Conclusions: A high percentage of Moroccan patients with AS (55%) reported being in PASS. PASS threshold for pain was unexpectedly high, possibly suggesting a high level of patients' tolerance to pain.